Gear shifting transmissions of motor vehicles are shifted or controlled in general using an actuating device located within reach of the driver. Actuating elements such as shift levers or selector levers are used regularly for this purpose, and are located, for example between the front seats of the motor vehicle or in other regions of the cockpit.
In the case of manually shifted transmissions in particular, purely mechanical actuating devices and transfer means are often still used between the actuating element and the gear shifting transmission. These can be mechanical transfer elements such as cables or linkages, for example, between the actuating element and the transmission. Newer manual transmissions for passenger cars usually include five or six forward gears and one reverse gear, wherein these six or seven gear positions of the shift lever are disposed, in general, in the form of an H shift pattern, grouped around a center, neutral middle position of the shift lever.
An H shift pattern for a mechanically actuated manual transmission often requires considerably more construction space for the actuating system in the region of the vehicle interior, however, due to the shifting travel and the selector travel required at the transmission, and due to certain actuating forces on the shift lever that cannot be exceeded for reasons of ergonomics, in particular compared to a selector lever of an automatic transmission or to a shift-by-wire control for an automatic transmission.
However, since different actuating systems must be provided for various variants of a motor vehicle having different types of transmissions, this means that the vehicle interior must therefore likewise be adapted to the construction space required for the actuating system, for example in the region of the center console, the cockpit, or the floor panel, depending on the type of vehicle transmission and, therefore, on the type of actuating system that is used. Therefore, depending on the type of transmission that is used, or on the type of actuating device that is used, this can result in the need to make complex changes to the aforementioned assemblies in the region of the vehicle interior, which is associated with correspondingly high costs. A further disadvantage that can be associated with the mechanical transfer of shift commands between the actuating device and the gear shifting transmission of the motor vehicle lies in the need for the cables or linkages to pass through the vehicle floor panel, the driveshaft tunnel, or the bulkhead of the motor vehicle. These passages are likewise structurally complex, and can also be disadvantageous in terms of noise production, the transmission of structure borne noise, and crash behavior.
Attempts have been made to circumvent these disadvantages, which occur in the prior art, by converting gear shifting transmissions of motor vehicles, including manual transmissions, to shift-by-wire actuation. The purpose of this was to obtain greater design flexibility in the vehicle interior in terms of the design and placement of the actuating device for the transmission. Due to the elimination of mechanical transmission linkage and spatially extensive mechanical actuating levers, it is hereby also made possible to provide the most uniform assemblies possible in the region of the cockpit, the floor panel, and the center console for all variant transmissions of a motor vehicle.
Even in the case of shift-by-wire actuating devices for motor vehicle transmissions, however, it is necessary to provide the driver with a realistic feel for the actuation of the transmission, for reasons of safety and ergonomics. It is therefore necessary that the driver be provided with visual feedback as well as clear haptic or tactile feedback regarding the current shifting state or operating state of the transmission when the transmission is actuated.
For reasons of ergonomics and safety, it is therefore particularly important that the driver receive clear haptically noticeable signals that certain shifting states or shift operations are not permitted at a particular moment in the form of the corresponding operating positions of the shift lever being blocked; the driver is already familiar with this situation from the use of fully synchronized mechanical manual transmissions, for example, with their rotational speed-dependent and speed-dependent synchronizer locks.
However, when gear shifting transmissions are actuated electrically or using shift-by-wire, the actuating element in the passenger compartment and the motor vehicle transmission in the engine compartment are not mechanically coupled in this manner. Instead, in the case of “shift-by-wire” transmissions, the shift commands are transmitted from the actuating device to the motor vehicle transmission using electrical or electronic signals, and the shift commands are then usually implemented at the transmission using electrohydraulics. Due to the absence of a mechanical connection between the transmission actuator system and the actuating lever, however, the transmission state, any shift interlocks, or impermissible shift commands can no longer react directly to the state of the actuating lever. Since certain gear positions are not noticeably blocked at the actuating lever, the driver of a vehicle equipped with a shift-by-wire transmission is unable to easily recognize that certain lever positions, gear selections, or shift commands may not be permitted in the current driving condition and therefore cannot be selected.
Depending on the state of the gear shifting transmission to be operated, and depending on other factors of the state of the motor vehicle, e.g. engine speed, vehicle speed, clutch position, etc., in order to implement the necessary haptic feedback in shift-by-wire-controlled transmissions, it is generally necessary to limit the range of operation of the actuating lever in an actuator-controlled manner and depending on the transmission state. In this manner, when the driver grasps the actuating lever, he can be notified in a haptically noticeable manner, even when the vehicle is equipped with a shift-by-wire-controlled transmission, that his shift request is not permitted and is therefore blocked, for example due to the current speed of the motor vehicle or due to a current operating state of the gear shifting transmission. It is therefore possible to prevent shift commands that cannot be implemented by the transmission at the moment, and that are detected by the transmission electronic unit and are not transmitted to the transmission from being engaged at the actuating element since deviations between the actual transmission state and the shift position that was engaged at the actuating element are not permitted.
To this end, the driver of a vehicle equipped with a shift-by-wire-controlled transmission must experience the same haptic reaction he would if using a mechanically actuated transmission—a manual transmission that includes transmission linkage, for example—when he makes an actuation attempt, in which shifting of the individual gears is blocked at the shift lever, in particular, depending on the speed. In this manner, the shifting of gears that are not permitted at the moment, or gear selections that cannot be shifted by the transmission at the moment are ignored electronically, and in fact are prevented at the actuating element using a mechanical lock even before actuation is attempted.
As described in US 2006/0016287 A1 or DE 10 2005 033 510 A1, for example, attempts have been made to implement locks of this type by equipping actuating levers of shift-by-wire-controlled gear shifting transmissions with a plurality of actuators or multiple-action actuators, and with appropriate lever elements or transmission elements to selectively block impermissible shift commands. These actuators and the lever elements or transmission elements they control are shifted depending on the vehicle state or transmission state to thereby limit the overall range of motion of the actuating element in accordance with the current drive state or transmission state.
However, if a plurality of different lever positions in different combinations must be blocked using actuators, then, according to the prior art, a complex locking mimicry is often required for this purpose. This has unwanted consequences due to the complexity and costs involved. Problems can also arise in terms of the available construction space in the region of the actuating device, and in terms of energy consumption and heat generation.
This applies in particular when the aim in terms of a shift-by-wire actuating device is to implement an H shift pattern, for example, to control an automated manual transmission. The latter is very difficult to implement using the lockout mechanisms known from the prior art in particular since an H shift pattern can include two and even up to four adjacently disposed shift gates, in which shift positions must be blocked or unblocked, depending on the state.